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Thursday, December 6, 2012

23andMe Ancestry Composition Examples: Part One

I am going to examine the Ancestry Composition chromosome paintings and ring charts from a wide variety of 23andMe members so that we can see how Ancestry Composition differs from the old Ancestry Painting, and how the results compare to what people know about their own ancestral background.

PERSON #1Known Ancestral Background: 4 German great-grandparents, one
Welsh great-greandparent, one Native American great-grandparent (probable European
admixture), one English great-grandparent, one Scottish/Ashkenazi Jewish
great-grandparent

Here is Person 1's original Ancestry Painting.

Person #1 has European ancestry from a variety of countries -- in Ancestry Painting 1 (hereafter referred to as AP1), all of this European ancestry is represented by the plain dark blue. Person 1 also inherited a number of non-European segments from his Native American great-grandparent, which are highlighted in orange. Overall, in AP1 this person gets a 96% European and 4% Asian score.

Here is person #1's new Ancestry Composition.

You can see that his European ancestry is now broken down into subgroups.

He has one Welsh great-grandparent and one British great-grandparent. Each one of these ancestors contributed an estimated 12.5% of person #1's DNA. He also has a great-grandparent who is part Scottish. Overall, he is approximately 30% British. His "British and Irish" score hits the mark almost perfectly -- 24.2%.

Person #1 is approximately 50% German. Ancestry Composition picks up on this DNA in several ways. His "French and German" score is 13.7%. Also, his "Eastern European" score is 4.3%. Historically, borders have changed & the German and Polish ethnic groups have interbred quite a bit. This means that Person #1's German ancestors likely had deeper ancestry that could be traced back to Eastern Europe, and this is what is showing up in Person #1's Ancestry Composition.

So, we're up to 13.7% French and German + 4.3% Eastern Europe = 18 of Person #1's total of 50 percent German ancestry is accounted for.

Where is the rest?

Not all of Person #1's German DNA is able to be tagged as uniquely and solely German. For more information about this, please visit this FAQ as well as this excellent guide that 23andMe has published. What we can conclude from this is that much of Person #1's German DNA is unable to be tagged as DNA that is found only in German -- therefore it is under the category of "Nonspecific Northern Europe" and "Nonspecific Europe."

Person #1 also has a small amount of Ashkenazi admixture. In AP1, this admixture remained undifferentiated from Person #1's European DNA. But Ancestry Composition has tagged it all perfectly. Person #1 gets a score of 2.4% Ashkenazi.

Ancestry Painting 1 was able to successfully differentiate Person #1's European DNA from his Asian DNA. But Ancestry Composition goes one step further -- it is able to accurately determine that Person #1's Asian DNA is Native American in origin. Before, with AP1, a variety of Asian DNA such as Chinese, Japanese, and Native American were all placed in the same category and unable to be differentiated from one another. But with Ancestry Composition, Person #1's Native American DNA that he inherited from his Native American great-grandparent is correctly tagged as such.

PERSON #2Known Ancestral Background: 100% Mexican

Once again, we see that Ancestry Composition has done an excellent job at further subdividing this person's DNA into different world subgroups. Previously, Person #2's DNA was categorized into just the three simple categories: Europe, Asia, and Africa. Just by looking at Person #2's AP1, you wouldn't really be able to guess which region of the world she originated from.

Ancestry Composition makes this much clearer. The generic Asian DNA from AP1 is now highlighted as being predominantly Native American in origin. We also see that a significant portion of Person #2's European DNA can be properly categorized as Southern European DNA, much of which can be further tagged as originating from Spain/the Iberian peninsula.

Before, with AP1, we saw generic European DNA plus generic Asian DNA plus a smidge of African DNA. That doesn't say much about this person's origin. But with Ancestry Composition, this person's mestizo heritage -- Native American plus Iberian -- comes through quite clearly.

PERSON #3Known Ancestral Background: half Bulgarian and half Turkish

It's a very similar story with person #3. His AP1 is quite similar to person 1's, so it's reasonable to suppose that, like person #1, he also has primarily European ancestry with a distant Native American ancestor. Just by using AP1, there's no way of proving or disproving this hypothesis.

Ancestry Composition comes through and delivers a strikingly different picture, though.

This person has a mix of Bulgarian and Turkish ancestry, and accordingly, Ancestry Composition clearly tags much of this person's European DNA as being Southern/Eastern European, with the lion's share tagged as originating in the Balkan peninsula.

Person #4's original Ancestry Painting lists her as being 100% European. This is perfectly consistent with what Person #4 knows about her ancestry, but is quite generic

Ancestry Composition zooms in a bit deeper and is able to readily identify all of the British Isles heritage that person #4 has. Her ancestral background is 100% British and Irish, and her Ancestry Composition score is 86.1% "British and Irish." The leftover portion is largely tucked into the "nonspecific Northern Europe" category, meaning that some of her British/Irish DNA is not specific to the British Isles, but is instead found throughout Northern Europe.

There are a couple of tiny segments showing a very small amount of North African ancestry. This could be statistical noise or it could be indicative of a trace amount of DNA from a historical migration pattern.

PERSON #5

Known Ancestral Background: African-American

One thing I want to highlight in this person's painting that I haven't previously discussed is the power of phasing. Phasing means separating your maternal complement of chromosomes from your paternal complement of chromosomes. Ancestry Painting #1 was entirely unphased, but Ancestry Composition contains a step in which the genome is phased (for more info, read here).

Separating the paternal side of your genome out from your maternal side gives you a clearer picture of what you are looking at in terms of your ancestry.

Here's an example, with AP1 on top and AP2 on the bottom. In AP1, it's a zigzag mess with tiny Asian, African and European chunks interspersed with one another. This is because the data is unphased. Phasing smooths it out dramatically and we can now see, for example, that this person inherited a large piece of African DNA from one parent on chromosome 5 and Native American DNA from the other parent. It's separated out rather than hodgepodged together like it was with AP1. This can potentially be a great help when used in combination with Family-Inheritance and Relative Finder -- phased chromosome painting may show more clearly what region a shared segment likely comes from.

That's all for now!

Check back soon for my upcoming posts, which will focus on the Ancestry Composition of these individuals:

Person #6:Known Ancestral Background: three quarters
German and one quarter Norwegian

12 comments:

Thanks Andrea :) I am curious why you are only showing the speculative vs standard estimates here? It might be worth pointing that out upfront as people like me will probably be comparing our standard estimates to these figures.

Nice overview, Andrea. I'm liking what I see of Ancestry Composition so far, but I think that they once again let us down on the African breakdown...the populations are there, I don't know why they don't have the confidence to use them. Some of it is a bit too conservative for my tastes...even on Speculative it ignores Middle East/West Asian and East European ancestry that every other test has picked up in me. But overall, it is light years ahead of what we've dealt with for the last 3-4 years!!

Based on the percentage of Native American #1 shows on average this would indicate that the great grandparent who was Native America was in fact 1/4 Native American (i.e. this person had a single Native grandparent or maybe two half native grandparents).

I think this is quite common in North American culture where the recall of a single native ancestor persists for some time.

I am 1/4 Mexican with a grandmother from the southwest and she passed down to me 13.5% Native American which of course came from many mestizo ancestors.

My mother who would likely be a 1/4 native has little to no knowledge of this.

"I think this is quite common in North American culture where the recall of a single native ancestor persists for some time."

Native American drops off the genome about 5 generations, It goes quickly, more so considering a person having 1 Native American ancestors. Doesn't make any sense.

"Based on the percentage of Native American #1 shows on average this would indicate that the great grandparent who was Native America was in fact 1/4 Native American (i.e. this person had a single Native grandparent or maybe two half native grandparents)."

Your math must really be bad and recombination. Going by this theory on example 1, the Native American grandparent being 1/4 Native American would put the testers ancestry at:

^ That is not correct. Recombination can play a big factors. Based on one fullblooded Native American grandparent, I've seen people with a great grandparent Native American test 3% and a sibling test 6%. 5%/6% is the median for a great grand. Most people with a great grandparent seem to test within those ranges. You can't base your ancestry on your numbers and apply them to other people's ancestry, especially since your native is from a multi-generational line.

Just about all African Americans get a percentage of Native American but Henry Louis Gates says the average black person who was a slave had never even seen a Native American and most African Americans have no Native American ancestry.If most African Americans have no Native American ancestry then why are African Americans getting Native American percentages.How do we know it the percentages are real or not?

Well there is at least one factor to consider! Remember about many runaway slaves that stayed in regions like the south? Many of these runaway slaves ended up in Native American territories and interacted with them. If the relations between both African Americans and Native Americans were mostly stable and compatible then obviously there were many interracial relationships between the groups.

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